OBJECTIVE: Our aim was to evaluate lung involvement in Crohn's disease (CRD) patients by induced sputum (IS). Extraintestinal manifestations are frequent in CRD, but lung involvement is rare. Induced sputum is a reliable noninvasive method of investigating the pathogenesis, pathophysiology, and treatment of lung disease. METHODS: Twenty-four CRD patients and nine control subjects (all nonsmokers) without respiratory symptoms were tested. Sputum was induced by 20' inhalation of 3.5% saline using ultrasonic nebulizer. Samples were studied by differential counts of 200 cells on cytopreps stained by Giemsa. T-lymphocyte subset analyses were done by FACS using three monoclonal antibodies: CD3 = total T cells, CD4 = T helper cells, and CD8 = T suppressor-cytotoxic cells. CD4/CD8 >2.5 was considered abnormal. RESULTS: Four patients did not produce sputum. Of the remaining 20 patients, seven had active CRD and 13 were in remission. They were divided into two groups: Group A patients had abnormal CD4/CD8 ratio of 6.7 ± 2.5; Group B (seven patients) had normal CD4/CD8 ratio of 1.7 ± 0.52 (p = 0.0001). The differential counts of IS samples were similar in both groups, but lymphocyte count was significantly higher in CRD patients than in the control group (13.2 ± 11.2 vs 4.8 ± 3.6, p = 0.036): There were no differences in spirometry, treatment, extent, or activity of CRD. CONCLUSION: Using a simple noninvasive method, we found that among CRD patients without respiratory symptoms there was a high (65%) incidence of lung involvement. (C) 2000 by Am. Coll. of Gastroenterology.